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Fire suppression in the last several decades has resulted in unprecedented accumulations of organic matter on the landscape, leading to an increase in large, intense wildfires. This study investigated the soil microbial community (using phospholipid fatty acid analysis) across recently burned forests on the eastern slope of the Cascade Range in Oregon to examine the effects this belowground community has on the growth of native and non-native plant species in severely burned “red” soil and in less severely burned “black” soil. Long duration, smoldering conditions creating red soils drastically altered both soil nutrients and microbial community structure. Changes in soil properties and biota affected plant growth in a controlled growth chamber, as well as vegetative colonization on red soil plots in natural field conditions. Differential growth was observed between native and non-native plant species when grown in soil from the two burn severities. Native plant growth did not differ between black and red soil, while non-native plants showed reduced growth in
red soil. Although it previously had been reported that fire increased the likelihood of invasion by non-native plant species in a burn area, these results do not support the notion that red soil conditions are more susceptible than moderately burned soil to non-native, invasive plant species colonization. While many factors in addition to mycorrhizal colonization and burn severity influence plant growth, such as soil nutrient availability, our results suggest that a variety of strategies allow plants to grow in disturbed environments. Continued monitoring of microbial communities and re-vegetation in red soil sites could further our understanding of the length of post-fire recovery time of severely burned red soil. |
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